The invention relates to a wind turbine rotor blade comprising a blade tip, a blade root, a leading edge, a trailing edge, a pressure side, a suction side and a cross-section, which changes from the blade tip to the blade root, wherein the cross-section is formed by an aerodynamic profile in the middle of the rotor blade and is mainly circular at the blade root. Such rotor blades are used in particular for wind turbine systems with a two- or three-blade rotor with a horizontal axis. They are connected at their blade root to a hub of the rotor. An assembly flange can be designed at the blade root of the rotor blade and the pitch angle of the blade can be designed to be adjustable with the help of a pitch drive.
Known rotor blades represent a compromise between the optimal aerodynamic shape, the requirements of the strength design and the attempt to create an economical manufacturing technique. In particular, the relative thickness of the used aerodynamic profiles must be selected based on strength considerations. A relatively small blade thickness of less than 30% of the profile depth, frequently between 18% and 15% of the same, can be used in the aerodynamically particularly important outer area of the rotor blades. The inner area of the rotor blades, which lies closer to the hub, plays a less decisive roll aerodynamically so that more deviation from the aerodynamic optimum and a relatively large blade thickness can be accepted in order to achieve sufficient rigidity. The aerodynamic profile then merges into the mainly circular cross-section towards the blade root. In order to improve the aerodynamic performance of the rotor blades on the inside, different approaches are known from the state of the art.
The use of a fin-like attachment extending longitudinally along the trailing edge of the rotor blade is known from document WO 02/08600 A1, the entire contents of which is incorporated herein by reference. The attachment is primarily located in a cylindrical connection area of the rotor blade, which connects a rotor blade portion arranged further on the outside and provided with an aerodynamic profile with the hub. In this manner, the otherwise aerodynamically ineffective connection area also contributes to the performance of the rotor.
A rotor blade for a wind turbine with an attached device on the pressure side near the blade root is known from document DE 10 2006 017 897 B4, the entire contents of which is incorporated herein by reference. The known attached device extends mainly in the longitudinal direction of the rotor blade. A so-called attached-device flow surface of the known attached device begins on the pressure side at a point of the profile where a tangent applied to the profile runs at an angle ranging from −20° to +20° to the designed direction of flow. The attached-device flow surface runs approximately at the angle of this tangent up to a trailing edge of the attached device that is different from the rotor blade trailing edge, to which a rear surface of the attached device connects, which leads back to the pressure side of the profile. Comparable attached devices are also known from documents EP 2 138 714 A1, the entire contents of which is incorporated herein by reference and EP 2 141 358 A1, the entire contents of which is incorporated herein by reference.
A rotor blade of a wind turbine, which is specially designed for a gearless wind turbine, is known from document WO 2004/097215 A1, the entire contents of which is incorporated herein by reference. Such wind turbines have a hub with a relatively large diameter. In the case of this known rotor blade, the aerodynamic profile of the rotor blade is continued mainly up to the hub, which leads to a very large profile depth due to the large profile thickness near the hub required for reasons of rigidity. In order to achieve this, the rear area of the profile is formed by an attachment.
A wind turbine rotor blade is known from document EP 1 845 258 A1, the entire contents of which is incorporated herein by reference, the cross-section of which has a concave pressure side addition portion in a transition area between a circular blade root and an aerodynamic profile. The rear end of this pressure side addition portion is connected with the trailing edge via a straight portion, which is aligned perpendicular to the profile chord and also belongs to the pressure side. The suction side of the known rotor blade is formed by a convex portion between the leading edge and the trailing edge, which merges into the straight portion at the trailing edge forming an outward pointing kink.